Apparatus for fault location on electrical conductors



.APPARA'IUS FOR FAULT LOCATION ON ELECTRICAL CONDUCTORS H. M. FRIENDLY 4 Sheets-Sheet Filed July 10. 1926 umtwn m Dec. s, 1931. H. M; FRENDLY 1,835,860

APPARTUS FOR FAULT LOCA'IION ON ELECTRICAL CONDUCTORS Filed y 1926 4 Sheets-Sheet 2 Inv enlbr Herhevfil-Friendlg ALU 8, 1931. M. FRIENDLY 1835860 APPARATUS FR FULT LOCATION ON ELECTRICAL CONDUCTORS Piled y 1926 4 Sheets-Sheet 4 Inveninr- H er]: EI1M'FI1 endly zfWM Allg Patentecl Dec. 8, 1931 UNITED STATES PATENT OFFICE HERBERT M. FRIEN'DLY, O]? CHICAGO, ILLINOIS; HILTON S. FRIENDLY AND (ZENTRAL REPUBLIO BANK'& TRUS'I 00., EXEOUTORS O)? SAID HERBERT M. FRIENDLY,

DECEASED APPARATUS FO R FAU'LT LOOATION ON ELEC'IRIOAL COND'U'GTORS Application filed July 10,

An object of the present invention is to provide a type of fault locating aparatus of the so-called Wheatstone bridge .general class, Which is particularly adapted for use by telephqne und telegraph wirechiefs,

though it has other uses'.

While elements of the present invention correspond to those of the so-called Wheatstone bridge, which is Well known, the structure and organization 0f the present invention is distinct-ly difl'erent, looking towards rapidly executing "tests and for obviating mathematical calculation 01 referen 'ce to formulw inr6ducing the test observation date .tothe desired uriits.

Refepence is macle t0 my Patents N o. 859,556 0f July 9, 1907 N0. 1034,609 of August 6, 1912; N0. 1,057817 ofApril 1, 1913. In view of the said patents, it is thought thatthe principles, operation a11d general adaptations of the present invention Will be clear from the descriptions to follow. The present invention employs certain basic principles disclosed in said patenjzs. However, it involves mechanical and electrical modifications not disclosed therein.

A salient object 0f the present invention is the provision of Ineans whereby the minimum of operations are required and the minimum of time in taking observation data is required; because in testing for faults, particularly on telephone and telegraph lines, time is an important factor in restoring service. Moreoer in instances, a time limit may be a cletermining factor in making the tesc. Again, due to a transitory fault concli tion, but a br1ef time may be allowed to take observations for data upon which the 100ation of the fault can be determined.

Inlocating certain kinds of faults in local efl'ect; this connecting tdgether conductively 0f the sides 0f the line at the time 0f making the test.

Obviously, the subscriber should 1926. Seriell N0. 121,667.

not be annoyed by knowingly aiding in the conducting of these tests. The present in- Vention enables the wirechief to call a subscriber whose line he wishes 130 have closed at the subscriber station, and after a response has been obtained from the subscriber (wherein the remote ends of the sides 0f the line are incidentally closecl 150 form a loop circuit) the necessary tesl;s to determine the location of a ground fault 01 cross with another conductor, 01 certain other tests, may be made While the wirechief simply occupies t he time of the called subscriber by verifying the telephone number callecl; tl1is conversation occupying, perhaps, from five to ten seconds. The subscriber, not suspecting that he has assisted in a testing operation, will have no reason to resent his being called. Moreover, the data obtained by the tester will be in terms Which will not require their applic atipn t0 formulae before having loca t1on s1gn1ficanc'e. That is to say, the instrunent Will be direct-reading in that results gn tl1e desired unit will be observable in the mstrqment. The present testing instrument 01' l r1dge will alsddisclose for ready obser- Vat1on the data 01 factors of the test as well as the direct-reading results.

he present invention provides a testing br1dge particularly adapted for use in 1003i;- 1ng faults by wirechiefs in charge of long distance toll lines, as .well as by wirechiefs in ch. arge of subscriber lines. Test-ing by wirech1efs is usually made under stress of denoralized service, so that simplicity in mak- 1nq the testing observations and rapidity and nechanical accuracy in arriving at rlasults m concrete terms is a prime desieratum.

Tl1e testing, instrument of the present invent1on may also serve as a milli-ammeter in deterrmning current strength; in fact the instrument is normally a milli-ammeter, but having the adaptability of a testing bridge for measuring resistances and for lpcating to the accompanying drawthe fault locating apparatusof the present invention, test battery, ground connection, test keys 0n the wirechiefs desk, a B operators plug leading from a pair of line test jacks ancl a subscriloers telephone line leading to a 1ine terminal jack cooperative With the B plug.

Fig. 2 shows a top elevation 0f the fault locating apparatus of the present invention embodied as a unit.

Fig. 2A shows a vertical section of the ratio arms mechanism shown in Fig. 2 taken along tl1e line A. 1

' Fig. 3 shows a bottom elevation of the apparatus unit shown in Fig. 2, but with the balance indicator (milli-ammeter) removecl.

Fig. 4 shows a detail of the movable scale .-1 also shown in Fig. 2.

- Fig.- 5 shows a partial seco1on of the upper or l to 1000ohm rheostat shown in Figs. 1 and 2. The section is taken along the vertical center line of Fig. 2.

Fig. 5A shows a side view of the wedge for securing the rheostat ring 13 shown in Fig. 5 to tl1e yokes 15.

Fig. 5B shows the front view of tl1e wedge 29 shown in Fig. 5A.

Fig. 6 shows a bottom plan of the parts shown in Fig. 5, but with the protecting cover and springs 362940 removed.

Fig. 7 shows details of the operating handle 14 and the stem 35 therefor shown in Figs. 1, 2 ancl 5.

Fig. 8 shows a detail of tlie stem 35 and the sleeve 37 showh in Figs. 5 and 7.

Vith reference to Fig. 1, it will be noted that the resistor 5 oining the terminals 6 and 7 is adapted to form two resistors or sot-ernoed A and B ratio-arms between the terminals 6 anal 7. The resistor 5 is merely indicative, so that the tappoints thereon do not purport to'exactly represent proportionate resistance values with reference to the resistor 5.

It will loe noted from the designations thatdepencling upon what tap-terminal a to e the contact-arm 8 is resting upon will determine the relativ values of the A and B ratio-arms into which the resistor 5 Will be thus diviclecl. Ancl, in vie w Of the well known represerltation of Wheatstone bridge schematic diagrzims, the ioortion of the resistor 5 between the contact-arm 8 and the terminal 6 Will be referred to as tl1e A arm, while'the portion between the contact-arm 8 and the terminal 7 Will be referred to as the B arm. The contact-arm 8 may loe revolvecl about its pivot by its handle 9 t0 at Will engage any one 0t the tap-terminals a to e, ancl t-l1e ratio of the resistance of the A arm to the resistance in t-he B arm Will be as numerically designatecl contiguous to the respective. tap-terminals.

It Will b'e noted that the possible ratios between theresistances of the A und B a1ms are 10 to 1, 1 130 l, 1 to 10,1t0 100,1 to 9 and 1 to 99. It Will also be noted that in the case of the 1 to 9 ratio the sum of the component parts equals 10, or otherwise, the first power of 10. In the case of the 1 to 99 ratio the sum of the component parts equals 100, or otherwiSe the se coi1d Power of 10. The valu e of the resistor 5 inay be 1000 ohms, or other c onvenient value; the values ohosen depending upon thovoltage of the test battery employed, the sensitiveness of the milli-ammeter near its zero point, as well as the resistanceof the circuits under test.

The rhe0statsl3 and 13', operated by handles 14 and 14, respectively, together form the so-termed adjustable-arm oi:' the bridge. The so-termecl adjustable-arm of the briclge therefore is tl1e portion between the terminal 7 and the test bincling-post 17.- 'Tl1e soindicating pointer 21 is rigidily attached to] the moving coil 20. A. magnet having poles N ancl S and c.orresponding attached nove. shaped pole-pieces N and S, respectively, influence the (301120 when thev latter is energized, in order to move tl1e pointer 21 variably responsive with the strength of current traversing the coil 20. The ridges n anti s in the pole-pieces N and S, respectively, aligning with the normal position of the coil 20 as shown in the clrawings in order to give tl1e coil 20 greater turning torque near the zero position. This is to insure a high sensibility and amplified movement at 01 near the zero position of the pointer 21, with relatively 10W sensibility at tl1e outside portions 0f the scale. Furthermore, this provision is to obviate or reduce possible damage to the pointer from abnormal currentin the coil 20.

Due to the pointer deflection from zero being.

a function of the unbalanced condition of the bridge arms in tests tlie tester is enabled t-o anticipate the degree of unbala'nce and quickly balance the bridge oircuits.

It Will be notecl that the test battery connected to binding-posts 22 and 23 is normally connected between the junction point (coutact-arm 8) of the ratio-arms and the binding-post G. The key Bais provided as an auxiliary or alternative means which may be used to apply the test battery to the bridge circuits if the key 27 is not used int-ermediate of the bridge binclingposts 17 and 18 an the line uncler test. Depressing button Ba Will tie one pole of the test battery to faulty 001 1- ductor binding-ost 17, as has been a Well ancl the resistance -termed adjustable-arm), are equal.

known practice in Wheatstone bridges, and

as shown in the patents cited at the outset.

By inserting the testplug into the line jack or the reverse line jack, the conductors of the B operators plug Will be serially included between binding-posts 17 und 18 when the receiver of the telephone on the line under test is removed from the switchhook 24 and the bridge test key is operated by the key lever 26; the latter key causing the test battery binding-post G to be connected With the binding-post 17, as does key Ba when button Ba is depressed. This causes the (ungrounded) testing battery current to flow over the line under test 2ind the bridge system, causing the milli-ammeter pointer 21 to deflect, provided the valu6s in the four arms of the bridge syst em are not in balance, so-termed. Disregardng the ground fault, since the test battery is n0t now grounded, the result of the test Will not be affected, regarclless of which line jack leading to the B- oper.ators plug 'the test plug is inserted into.

If itis assumed that the contact-arm 8 is in engagement with tap-terminal a as shown in the drawings, the A and B arms will hzwe equal Value so that the potential at the terminals 6 and 7 Will be equal only when equal current strength traverses the A and B arms.

This latter condition Will only exist when the' resistance included between the bindingposts 17 and 18 involvin g the loop 0f the line under test as one brauch (so-termed X-arm), introduced by one or'both rheostats 13 and 13, as the other branch (so- The rheostats 13 and 13 rheostats (er only one of them) have been adjusted until the pointer 21 comes to zero position, as drawn, and wherein the current from the test battery is then divided equally (Wer the A and B arms, and the line or X- arin and the adjustable-arm, respectively, the

adjustablearm involving the rheostats 13 and 13', the total indicated included ohmic resistance v'alue in tlierheostats 13 and 13' will exactly equal the X-arm ohmic resistance.

If. it is assumed that the contact-arm 8 is in engagement with the tap-terminal f, the' ratio of the arm to the B arm will be 1 to 10, so that to obtain a balanced condition 0f the bridge system with the -test batt-ery ungrounded the total value introduced by the rheostats 13 and 13 sistance of the line under test; that is, the res'iStance of the line under test (X-arm) will be the indicated zidjusted numerical value of the said rheostats, aftr pointing ofl' one dec' imal place to effect the division by ten. In the same manner, if the contact-arm 8 is placed 0n the tap-termii1al d, the ratio of th A arm to the B arm will be 1 to 100, so that 130 obtain a balanced condition the total value 'nine.

are graduated. 'Wl1en Will be ten times the re- -the B arm Will be 1 to 9, so that to obtain a balanced condition,the total value introduced by the rheostats 13 and 13 will be nine times the resistance ofthe line under test; that is, the resistance of the line under test Will be the inclicated numerical adjusted value in the rheostats 13 and 13, after dividing by Ii[owever this latter ratio not being a decimal ratio, will not usually be chosen for determining the loop resistance simply. It has other objects, as Will appear presently.

It will be clear that if the switch CR' is operated wherein the normal short-circuit is remved from the check resistor 19, it will be equivalent t0 adding 1000 ohms resistance in series with the line conductors under test; more pa'rticularly, the conductor of the line under test leading t0 the binding-post 18.

Assume that tly.e test plug is insertecl into the jack l-eading t0 the .B operators plug, and th'e B operators plug is then inserted into the linei terminal jack, and the key lever 26 is thrown to operate the bridge tesc key. It Will be noted that under this conditi0n the line conductor having the ground fault will be the one leading direct to the binding-post 17. Hand the test plug been' inserted into the reverse line j ack, this faulty line concluctor would then lead direct t0 binding-post 18. It is necessary, in making the Varley loop test for a ground fault (or cr0ss fault which may be resolved into an essentially equiv alent fault condition by grounding one of the crossed conductors) to have the faulty conductor lead directly t0 the binding-post 17 which is designated Faulty. This is so the faulty conductor Will be in direct, adjacent connection with and in series relation with the rheostats 13 and 13, the requirem-ent 0f' which will appear presently.

Assume further, with relation to the last -foregoirigassumption, that the contactarm branch ed path to the ground fault through the A and B arms, wherein the A arm has one-tenth the ohmic value 0f th'e B arm, as follows: From terminal 6 one said branch is through the n0rmally closed contacts of the 15 ammeter Will inclicate unequal potential between terminals 6 and 7 unless ten times as much current from the test battery traverses the branch including the A arm is that traversing the B arm, and this will only ensue 20 when the path traced through the B arm and.

the ground fault includes ten times as much resistance as the path through the A arm to the ground fault. If it is assumed (though not neoessarily so) that the line conductors of the line under'test are approximately 0f the same resistance per unit of length, and

' of approximately the same length, it Will be obvious that resistance will need to be intro duced by the rheostats 13 and 13 to bring about the balance of current potential between the terminals 6 ancl 7, since"it is improbable (as will be assumed for the present) th'at the resistance to the fault from binding-post 18 on the faulty conductor is less than one tenth 35 the resistance from the fault through the tele= phone to the binding-post 17. The total value of the resistance introduced by rhedstats 13 ancl 13 to balance with the point of fault on the line used as the fulcrum, and with the test battery grounded will be referred to as the r resistance.

The Wall known equation of the Varley loop test where unequal ratio-arms values are employed is:

BL-Ar dmtance m ohms to the fault (from the binding-post 17) 011 the faulty conductor, wherein B and A denote the numerical values of the A and B arms, respectively; L denotes the resistance 0f the line under test (including the receiver off the switch-hook) between the binding-posts 17 and 18; r denotes the value includecl by the rheostats 13 and 13' balanced condition last referred to with the test battery grounded. So, if the loop resistance of the line under test is, for ex the tests referred to for determining simple resistance. in the X-arm with the test battery ungrounded, or this resistance is known to the tester from previous determinations, ancl the value of r as last determined (with to effect the ample423 ohms,'as determined by one of 1,asa,seo

battery grounded) is, for example, 3691, the equation when substituted becomes:

0ut to the fault on the faulty conductor from binding-post 17.

If any other ratio between the A am] B arms were taken when balancing with the test battery grounded, the substitution would be made in the san1e manner For example, if the ratio of resistance between the A and B arms is taken as 1 to 9, as would ensue if the contact-arm 8 were moved into contact with the tap-terminal b, and the value of r (with test battery grounded) 1s then observed to be 3317, the substituted equation becomes:

1+9 49 ohms as the resiStance out to the fault on the faulty conductor from binding post 17.

If said acljusted value 3317 is not removed from the rheostats 13 and 13 and a loop resistance observation (with test battery ungrounded), is then taken by inc reasing the value involved in the rheostats 13 and 13, witl1 the handles 14 and 14' undepressed and without first restoring the respective rheostats 13 and 13 to zero resistance value, it Will be found that 490 ohms additional will have t0 be i1itroduced to efl'ect a balance of the po-inter 21 of the milli-ammetor. This is ten times the ohmic resistance to the fault on the faulty conductor. That is, taking a balance with the test battery grounded and with the 1 to 9 ratio-arms seting, sind then taking a balance with this same 1 to 9 ratioarms setting, laut with the test battery not grounded, the difierence between the two balance values introdu ced by the rheostats 13 and 13' in the successive two tests where a balance is obtained in each instance, Will be ten times the ohmic valuefrom the bindingpost 17 to the fault on the faulty conductor. So, in choosing tl1is ratio-arm relation of 1 to 9, a first balance may be taken with the test battery grounded, and a second balance then taken With the test battery looped (wherein the last ohmic value will inherently always be as large or larger than the former), and by pointing off one decimal place from the diiference in the observations, obtain the ohmic value included from binding-post 17 t0 the fault on the faulty concluctor connected directly thereto. This is regardless of the disparity of the ohmic value per unitof tial of th ground fault will not be a factor in quired in imparting a, full and clear undere the result standing of the present invention.

It willbe clear presently, that when mak- With reference to Fig. 2, arts schematiing the last assumed test Wherein'the contactcally shown in Fig. 1 are shown in detail arm 8 is in contact with the tap-terminal b, correspondingly indexed. The scale 31 is and Wherein the ratio 0f the A arm to the B made of thin metal as shown in section in arm, 'is 1 to 9, that the actual or .numerical Fig. 5. This scale 31 is fastened by four Vahie 01" the l00p resistance of the line under screws 32 130 the mounting plate 33. The test with fest battery ungrounded is not scale 1 fits revolvably within the scale 31 graphically r0corded or noted, nor is it necesand is held against being removed by a bevsary to graphically record or note the a'ctual eled edge 34 cooperative with the inner cirnumerical value of the r resistance required curnference of seale 31. The scale 1 is shown to balance one ortion of the subscriber"s loop in detached detail in Fig. 4. The scale 31 is against the otlier with the point of ground shown only partly graduated,but it is 00 be fault as the fulcrum. However,the diflerence und rst ood that the graduations extend all in these observmtions, as read directly from the way ar0und; each indicated division the bridge, is considered and divided by ten corresponding to 50 ohms, so that the 20 V P0intirlg 0ff 03119 decimal P The firSt divisions comprise a range of 1000 ohms in adjustment to balance 0f the rheostats 13 th l d embodiment. Th scale 1 has and 13 Wherein the test battery i gr011ndd divisions and graduations radial with the 35 gives the numerical value of r required by d ti ()f scale 31, w 1l a having the Varley loop 'equation, but not noted by g du tion f one-half values and may the testeras an element of the calculation, h oth r not hown.

since this value is only used to set up a condi- B reference t Figs 5 d 8 th c t tion i the i i Cf th i g o a b tion of the stem 35 and the handle 14 and coquent observation of the specifie line under Operating Parts th r of ill b und rstoo d in t6 The Vahle 0f C1111 be Zer0 bllt it view of the descriptions to follow. The innever haVe a neg ive V ll in an 6 sulated point 0f the stem 35 normally rests test. If the observation should lead to a On t.h spring 3 th t thi' i gthrough negative value in any setting of the ratioit t j keeps th t 35 at i i arms, a higher ratio as between the A and B ti as h n Th t 35 i fi id1 f arms Will required in Order t0 Obtain a tened to or made integral with the handle 14 f% 0T the Check 19 l need by moulding the said handle on the said stem, t0 be 1ntroduced. Th1s negative value can th h dl b i f bly d f i l t only exist if the resistance t0 the fault 0n the i materia1 A S1eeve 7 fits revolvably bridge does not behave difl'erently from Well known Wheatstone bridges when used for 35 by t conductol from blndlng'post 17 18 through the 'mountin -plate 33, positioned l than (Wer the good Conductol' from by the shoulder 38. he sleeve 37 can thus p 18 around the Temote d Q the be telescdped into the handle 14 as shown l1ne under test t-o the fault, as can oceur 1f the b h dotted 1i in F 7 h h Stern faulty condactor is 0f relativel; high resist- 35 is moved downward by depressing ance P un1t 0f length Whereln the handle 14 against; the tens1on' 0f the spring Conductol' iS P test K a 3 36, wherein the spring 36 is disengaged from conductor 0f relat1vely low res1stance per h t e sprin 39 and engaged with sprin 40 as 0f length- In th1s respecta the Present indicated by the dotted position of spr%ng 36.

A finger 42 is rigidly fastened to the stem he finger 42 passing through the stem 3' the Wen kI1OWI1 Varley p fest} In 35. The sleeve 37 has an elongated hole43 fact thereferrefito test the Present br1dge in the right-hand side to admit the finger executes1SeSSent1auyth?Vafle}h0Pt stbut 42 and to permit the stern 35 carrying the .Where1n the present br1dge, through 1ts pefi 42 to be pushed or depressdr down 115 cnliar eonstruc tion and ratio-arm adapta- ?d Th Stem 35 may b turned d k 5 y Process m terms wise from the drawn normal position by the of the des1red 11n1ts 1nc 1dent t0 tak1ng.the obhandle 14 d returned to normal iti servations for the Varley loop data of the cirat Will b turning th h dl 14 t cuit conditions with respect to the line uni A retaining i 4 Passes 1 der testthrough the stem 35 flush with the lower face It is thought that in imp'arting a full of the mounting plate 33 to limit the upward derstanding Cf the theory and Operation movement of the said stem, and a stop-screw the present. bridg n SO 1 3S reflS0lls 37 is set into the sleeve 37 at right angles to the results hereinbefore generally sei; forth th i 44 t prevent the sleeve 37 baing freeis c0ncerned, a fuller discussion will not be ly removed, as otherwise the Stein 35 and required, since my patents made of referenCe sleeve 37 would' be subject to being lifted at the outset sets forth the theory quite upward,clear of t-he mounting-plate 33. The comprehensively. Therefore, actual results pin 44 extends through the slots 44 on op-\ rather than reasons for them, will only be reposite sides of the sleeve 37 as shown by the 1 the pointer alle finger which the point 45 of the finger 42 will regdotted lines in Figs'. 5, 6 and 7, so the pin 44 also serVes to revolve the sleeve 37 carrying wiper48 'when the stem 35 is revolved by thehandle 14.

/It will be noted that the finger 42 ha s a curved free end which has a wedge-shaped oint 45. Cooperative with the said point of 42 is a notch 47 of the sca le 1 into ister when the handle 14 is depressed, which latter operation incidentally operates the spring 36 into its dotted osition.

It will thus be clear that when the handle 14 is turned while depressed, the scale 1' will be carried through a, corresponding angular distance. Also, that when the scale 1 is being moved by the finger 42 the spring 36 will be in its dotted position 36.

The wiper48 engages the to edge of the wound circular' rheostat 13 (a so indicated schematically in Fig. 1), so as the stem 35 revolves from normal position resistance will be introduced by rheostat 13. The wiper 48 is seoured to the sleeve 37, but is insulated therefrom by the insulation bushing 49. A coil conducting-spring' 50 has one end attached to the insulated pin 51, which latte r is set into the mounting plate 33, and the other end of the spring 50uis attached to the pin 52 whi0h is set into the wiper 48, so that the pin 51 is permanently electrically tied to the wiper48 and both the pin 51 and the wiper 48 are insulated from the mounting-plate 33. This arrangement is provided so that a solid electrical connection of unvarying resistance is provided to the wiper 48.

A ointer 54 is rigidly fastei1ed to the upper ace of theshoulder 38 by screws, brazing, or any suitable method, so that it will indicate the angular position the stem 35 and the wiper 48 is turned from the normal position shown in the drawings.

A stop 56, which is the head of a.downwxdly tapered machine screw, prevents the scale 1 moving pa'st normal posit1on when returned to normal when the handle 14 is turned counterclock-wise wherein the end of 54 will engage the screw 46. The tapered head of the screw 56 permits ready adjustment of the scale 1 to zer'o osition by turning the serew 56 one way or t eother as required. The screw 46 is similar to screw 56 and can be turned 130 adjust the zero position of the pointer 54.

From the foregoing, it will be clear thar the handle 14 can be depressed before turning so that the end of the finger 42 will engagie the right-hand face of the notch 47, so that when the handle 14 is then t'ur'ned clock-wise the scale 1 and tl1e wiper48 Will correspondingly revolve, while the spring 36 will assume the dotted position 36. Then, if

the downward pressure is removed from the handle 14 to cause the end of the finger 42 to disengage the notch 47 and the spring 36 to balanoe with the attery grounded was obtai'ned, while the graduation on the rin% 31 opposite the pointer54 when the handle 4 is brought to the final stop in the clock-Wise movement, will indicate how many ohms are introduced by t-he rheostat 13 at thattime.

It is not thought necess.ry 01 desiredto detailthe operation of the designated Thousands dial beyond stating that a prime is added to the index numeral of parts corresponding to parts -of the designated "1 to 1000 dial. In place of using a wire coil circular' rheostat as 13, the rheostat 13 is made up of nine 1000 ohms resistor coils 61 to 69 connected in series wherein contact points 71 to 79 are cooperated by wiper 48 to introduce the said resistor coils in series in c0rrespondience with the tap-contact point 71 to 79 the wiper 48' is restmg upon. The wiper 48' normally rests on contact 70 wherein no resista'nce is introduced. Thus, in place of introducing srnall ohmic val1'1es involved in -the respeclsive turns of wire of the rheostat 13 directly engaged by the wiper 48, the resistor coils 61 to 69 of 1000 ohms each are successively introduced in series by the wiper 48' by steps of 1000 ohms as contacts 71 to 79 are engaged by wiper 48'.

then 'indicate how many ohms be clear that where the resistance value required to efl'ect abalance is greater than comprehended by the rheostat 13, the rheostat 13 will be brought int0 requisition. For examif when making the first balance with the handle 14 de'pressed (and' this will always -be the condition of the first observation in a Varley 100 test wherein the test battery will have one o its poles (the'negative in the exampled instance,) applied to ground, no balance ean be secumged, even by turning the handle 14 (clock-Wise) until all the resistance (1000 ohms in the exampled instance) of the rheostat 13 has been introduced, the handle 14 is revolved back (counter-clock-wise) to zero position and the handle 14 depressed and then turned until the milli-ammeter indicat-es a balance has been passed. That is, that too much resistance has been introduced. The handle 14 is then turned counter-clockwise so that the wiper 48 rests on the first antecedent contact 71 to 79 and the handle released so that spring 36 assumes its norquired. It is the line under test will ohms will be required to eflect the balance, the

' balance can be efiected by then turning the handle 14 cloek-wise frorn its zero position. When the balanced condition is attained, as indicated by the inilli-ammeter, the handle 14 will be released so that the spring 36 can restore to its normal position.

Assume that the point of balance is 0btainied when the pointer 54 is opposite the graduation indicating 673 ohms. Then, the combined resistance introduceed by rheostats 13 and 13 is 5673. This operation will be the sa1ne-regardl'ess of the ratio value used, though it is obvious, in yiew of 1ny patents made of reference a@ the outset, that the ratio value as between the A.and B arrns will directly atfect the amount of resistance required to efl'ect a balance. For example, if a ratio of 1 to 99 as. between the A and B ar1ns were used in the observation requiring the 5673 ohms to eifect a balahced condition, this amount of resistance would be reduced'had a smaller ratio, such as 1 to 9 or 1 to 1 been chosen, but, of course, not in direct relation. The ratio chosen will depend upon the resiStan'ce and positionof the fault in the line under test, the resistance of the loop under test, aswell as the degree of accuracyrenot taken into accouht by the tester at this stage of the test.

The adjusted value obtained as last desbribed corresponds to the r element appearing in the Varley loop equation. Now, to obtain the-final balance, involving the L element appearing in the Varley loop equation, the handles 14 and 14 Will be successively revolved clock-wisefrom where left in making the first observation, but this time without depressing the handles 14 or 14, and a balanced condition sought as before,since the circuits will to the 'springs 36 and 36 being at normal wherein the test battery is ungrounded. The resista'nce to the groundfault from the faulty post 17 on the faulty condi1ctor Will be the sum of the readings indicated by the pointers 54 and 54 0n t h movable scales 1 and l, divided by 2, 10 or 100, depending upon if the ratio 0f the A ratio-arm to the B ratio-arm is 1 to 1', 1 to 9, or lto 99, respeotively. It Will be noted that the scale 1 hs graduations in half values radial with the full values. This is to make the division by 2 more convenient when the 1 to 1 ratio is used. Where higher accuracy is desired, the 1 to 9 or 1 to 99 ratio between the A and B arms Will be employed, as the rheostat 13 Will then ordinarily involve most of the resistance introduced, the eoils of which may be calibrated to greater accuracy than the wound rheostat 13. However, in most instances the resistance o f come within the range of the 1 to 1000 ohm rheostat so that a Varley loop test with it alone may be made in a few 5 seconds.

be found out of balance due It will be olear from the last test described that where the Varley loop test is to be Inade, the A and B arms. are first set to the-desired ratio. Then the handle 14 is depressed to operate spring 36 to ground the test battery, while at the same time turning the handle 14 until a point is reaehed whe1e if it is turned further the milli-ammeter Will indieate a reversed out of balance condition. The pressure on handle 14' is 'then released so that spring.36' restores and scale l is disengaged by the finger 42. The handle 14 is then depressed to operate the spring 36 to ground the test battery while at the same time turning the handle 14 until a point is reached whereat the milli-ammeter needle 21 Will indicate a balanee of the -circuits. The pressure on the handle 14 is then released so that the spring 36 retores and the scale 1 is disengaged by the finger 42. The rheostats 13 andl3 110W involve the so-termed r resistance observed when making the well known Varley loop test with bridges heretofore used and Wherein this data is applied to the usual equation forsuch herein before given. However, the tester takes no account of this r value which is left indicated by the elf-normal position of the scales l and 1. v

The next Operation is that of balancing the .bridge with respect to the loop resistance of .That is, the last observation will include all the resistance introduced in the first observation, with any additional resistance required. The reading taken from the movable scales l and 1 as indicated by the pointers 54' and 54 will irepresent the distatnce tothe g1ound fault on the faulty conductor. However, this value will havet0 be divided by 2, 10 or 100, depending upon if the ratio of the A arm to the B arm is 1 to 1, 1 t0 10 or 1 to 100, respectively.

If an ordinajry loop resistance measurement is to be talren, wherein the resistance of the bridge leading-out oonductors to the B o'perators plg is to be subtracted, the ratioarms setting inay be 1 to l, 1 to 10 or 1 to 100. The bridge leading-out conductors will he short-circuited at the B operators plug. The two rheostats 13 and 13 Will then be adjusted witho.ut depressing the handles' 14 and 14 (rheostat 13 being adjus'ted first) in order scales 1 and 1 register radially with the ad- -justed position of the pointers 54' and 54.

The short-circuit is then removed from the leading-out eonductors so that the line under fies't Will be included befween the posts 17 and 18 and the rheostat 13' adjusted; followed by adjusting rheostat 13, but without first restorreferer'1ce to these scales to obtain the net loop ohmic Value to the line under test. That is, if a 1 to 1 ratio of the A arm to the B arm is used, it Will be the numerical value exclusive of the resistance of the leading-out couductors. The indicated reading on the scales 31' and 31 Will represent the total value between the posts.l7 und 18, which includes the bridge leading-out conductors to the B operators plug.

If the ratio of 1 to 10 or 1 to 100 had been used betweentha A arm and the B arm, the reading of the scales 1' and 1 combined or 31' and 31 combined will be divided by 10 or 100, re'spectively. paar that if a number of lines are 110 be measured for loop resistance wherein the same ratiobetween the A arm and the B arm is t;o be retained, the false zero determined by the position of the scales 1' and 1 will be used 'as a starting or zero point in each measurement, and not necessarily the absolute zero point as shown by the-position of the pointers 54 anal 54 in the drawings. Changing the ratio between the A arm and the B arm.will, of .course, requiria a new adjustment to false zero for the scales 1' and 1. Under this metho(l of taking loop reSistance measurements the oridge will show the leading out conduc tor resistance (represented by the false zero oflF-normal osition of the scales 1' and1) and the net under test loop resistance, with due regard to the ratio between the A. and B arms.

The rheostat '13, consisting preferably of a spiral coil of resistor wire bent into circular shape, is hold to the mounting-plate 33 by two yokes 15 wherein f011r insulation wedges 29 shown in detail in Figs. 5A and 5B are applied; one at each end of each yoke, showirin Fig'. 6. A sheet-metal strip 30 is secured by pins 31 to a face of.the Wedge and bent over after the wedge is sei: into position,

shown in Fig. 6, so that the wedge cannot be removed without straightening the beutover portion 30. Theyokes 15 are insulated by sheet insulation, o1 other, w here they come into contactwith the rhedst-at winding. The coils of the rheostat 13' may be simple resistor coils, such as have been used in well known Wheatstone bridges.

The milli-ammete'r is secured into p1ace by-means of four bolts 55 by nuts 57, wherein there are washer-plates 58 on the upper side It will therefore ap- -plate 33. The milli-ammeter pointer 21 moves over the scale 25 visible from the top.

Thecontact springs 36, 39 and 40 are insulated.- from each other and mounted on a washer-plate 88, Which latter, with springs and insulating separators are attached by screws 41 to the yokes 15. The employment of the springs 36, 39 and 40, operated by the stem 35, and also tlhe springs 36', 39' and 40', operated by the stem 35' are salient features ofthe present inventiori, whereby the test battery can be grounded incidental to depressing either handle 14 and 14' in order to engage' the scale 1.01 1', respectively.

Another salient featur'e of the present inventio n is the special shaping of the polepieces N and S of the m1lli-ammeter magnet 53 to make the sensitiveness of the milliammeter more pronounced ab and near the zero position.

In case it is desired 130 determine the current strength flowing in the line under test wherein a battery source, not shown is'included in the path of the test plug conc1uotors, the key 1ever 26 will be thrown to operate the milli-ammetdr key. Assuming that under the condition the circuitsof the bridge proper are as shown in the drawing Fig. 1, it will be seen that the milli-ammeter winding 20 and series resistor 20 will be shunted by the resistor 5, but in series with the line under test, and being graduated (so read in milli-amperes in the present exampled instance will indicate the current flow over the test plug couductors in milli-amperes. Thus, the present in'vention, as stated at the outset is, in fact, normally a milli-ammeter, but having adaptatio'ns for using it as a testing bridge Wherein the Var1ey loop test can be made, as well as ohmic resistance determined by the Wheatstone bridge method.

The ratio-arm adjuster having contactarm 8 is operatodby handle 9, designated Ratio wherein the contact-arm 8 successively engages the tap-terminals a, b', c, d, e and f, and continuously engages the conducting ring 86; the latter being conriected at lug 88 to conductor 7 7 shown in Fig. 1. T he said tap terminals and ring 86 are mounted 011 an insulated member 87 which is separated from the mounting-plate33 by four sleeves 80 which haye four machine screws 81 passing through them into the mounting-plate 33. The pointer 83 is rigidly 'secure d to the .ste m 84 with radial correspondence with the contact-arm 8, so that it will indicate on the upper face of the mounting-plate 33 the loca- Ition of the contact-arm 8 with respect to the and a flat surfaoe respect to the stem 84, so far as any turning of the stem 84 aboutits axis is concerned.

- The handle 9 is rigidly attached to the top reverse test (out over the end of the stem 84. It will thus be olear that the handle 9 and the oontaot-arm 8 can be continuously turned in either direction at will in setting the ratio-arms involved in resistor 5 With any indicated ratio-arm relation.

The check resistor 19 is introdced by depressing the self-restoring key button CR to operate key CR when it isdesired to introduce more resistance in the line conductor leading from the binding-post 18. This may (but not necessarily) be when the faulty conductor is adjacent to binding-post 18 in a good conductor) and it is desired t0 make, the resistance betweexi the binding-post 17 and the fault less than the resistance betweenthe binding-post 18 and the fault, having in mind that when a ratio between the A and B arms of 1 to 1 is used the resistance from the bindingpost 17 to the fault must be lower or as low as the resistance from the bindingpost 18 to the fault in order to execute a test, and also having in mind that in practice both conductors in a loop under test may not have the sarne cross section, resistance per unit of length, or length. The check resistor 19 thus lends itself to, in eifect, increase the resistance ofthe good conductor (er the faulty conduotor if it is adjacent to the binding-post 18 in a reverse test) if it has a relatively low resistance which, due to the location of the fault, may make the resistance from the binding-post 17 to the fault greater than the resistance from the fault to the binding-post 18. Under the latter condition, without the check resistor 19 included, a balance with a 1to 1 ratio betvveen the A and B arms could not be efi'ected, beoase adding resistance by rheostats 13' and 13 in the arm adjaoent to the binding-post 17 would then only increase the unbalance.

The check resistor 19 thus lends itself to making a reverse teSt using a 1 to 1 ratio between the A ar1d B arrns wherein the su1n of the conductor resistanoes to the fault out over the respective two conduotors of the line under test should equal the loop resistance, if a single fault exists. One of the latter tests Will require that the resistor 19 be introduced in order to meet the stated condition applied to) will not always be the one leading to the sleeve spring of the line jack, and in that case the reverse line kick will be employed in order to place the conductor it is deslred to measure out to the fault upon adjacent to the binding-post 17.

- The sorews 90 shown in F ig. 2 are for fastening the protecting cover 2 to the mounting-plate 33; lugs thrown out from the cover 2, not shown, being threaded to receive the screws 90.

The bearings for the spindle of the coil 20 of the milli-ammeter are not shown in order to simplify the drawings, but any desired known method -may be employed, the milliammeter not involv1ng invention over well known milli-ammeters ridges n and s in the respectively, the object-s of which have been set forth.

It has been stated that the mechanism for operating the rheostat 13 is like that for operating rheostat 13. While this is true, in general, the meohanism for rheostat 13 below the mounting-plat-e 33 diflers in detail. For example, the shape of the wiper 48' which makes contact upwardly thus obviates the use of a screw c'orresponding to 37 Also, the yoke 15 c orresponding to one of the yokes 15 is fastened by four screws 16 (liexcepting, as to the rectly to the mOunting-plate 33. The sei: of

springs 3639 40 are mounted by screw 11 to the yoke 15 so the spring 36 has the same relation to the end of the stem 35 as spring 36 has to sirr'1ilar stem 35. The eleotrical counections with relation to coils 61 to 69 are shown in Fig. 1.

The bridge test key and the milli-ammeter key are only two of a possible number of keys operatively associated with the test plug. For example, there would usually be a listening key for connecting the wirechiefs telephone tl1rough condensers to the conductors of the test plug so the wirechief rnay listen or talk over the oonnection to the subscribers telephone while conducting a test of the subsoribers line, the condensers 1naking the wirechiefs listening taps opaque to the direot current fro m the test battery. The ridges n and s of the milli-ammeter pole-pieces may be varied in shape. For example, the edges of the ridges may protrude a less distan'ce than the center. That is, the center of the ridge parallel with the axis of the moving coil willcome nearer to the ooil than the edges. Moreover, the edges of the ridges may ourve the opposite way from that shown in the drawings, all depending upon the characteristic scale graduation desired. The present invention is capable of de,- tailed modification without departing frorn its soope as defined by the subjoined claims; for example: The stem 35 in place of being circular in oross sectionmay be fltecl lengthwise in order toreduce the friction against free endwise movement. Again, the fric pole-pieces N and S,

tion against this endWise movement may be reduced by rolle'r 01 ball-bearings. The sleeve 37 may be revolved in a ball-bearing in place of the simple hearing shown, in order to permit it to revolve more freely. The movable scale 1 may revolve on a ball-bearing concentric with its axis, in order to make it revolve more freely, in place of revolving within its periphery as shown. The said bearing changes Will promote ease and rapidity of operation in executing teste.

Having set' forth an exemplary embodiment of the invention, what I claim is l. In a rheostat, a resistor, a circuit adapted for including said resistor, a Wiper for making contact along the resistor so as to introduce resistance of said resistor into the circuit, a graduated scale f01 indicating the resistance included by the resistor through the agency of the wiper movement, a handle for operating said wiper, means for operating the scale by the handle coincident with operating the wiper, means for further operating the wiper by the handle in a second stage movement to introduce more resistance loy the resistor without further operating the scale, and means whereby the graduations on said scale as defined by the final Position of the wiper will numerically indicate the value 0f the resistance introduced by the resistor only loy the second stage of its 1hovement.

2. In a rheostat, a resistor, a circuit adapted for including said resistor, a wiper for making contaet along the resistor so as 130 introduce resistance of said resistor into the circuit, a movable graduated scale for indicating the resistance included loy the resistor through the agency of the Wiper movement, a handle for operatmg said wiper for thereby introducing resistance by the resistor, a catch-finger of said handle, means Whereby depressing the handle by pressure will engage the catch-finger with the movable scale, means whereby then moving the handle Will correspondingly move the scale and wipe1, means whereby removing the pressure from the handle Will disengage the catch-finger, means whereby then movlng the handle in a second stage moven1ent will correspondingly move the wiper while the scale remains where last moved, and means whereby the graduations on said scale defined by the final posi tion of the wiper will numerically indicate the value 0'l the resistance included by the resistor only by the second stage of its movement.

3. In a rheost-at, a resistor, a circuit adapted f01' including said resistor, a wiper for making contact along the resistor so as to introduce resistance of said resistof into the circuit, a movable graduated scale for indicating the resi'stance included by the resistor through the age'ncy of the wiper movement, a handle for operating said wiper, a catchfinger of said handle, means whereby depressing the handle by pressure will engage the eatch-finger with the movable scale, a-nd means whereby removing the pressure fiom the handle will disengage the catch-finger.

' 4. In a rheostat, a resistor, a circuit adapted for including said resistor, a wiper for making contact along the resistor so as to introduee resistance 0f said resistor into the circuit, a movable graduated scale f0r indicating the resistance included by the resistor through the agency of the wiper m0vement, a handle for operating said wiper, a catchfinger of said handle, means whereby depressing the handle by pressure Will engage the catch-finger with the movable scale. means whereby removing the pressure from the handle Will disengage the catch-finger, and means whereby then moving the handle will correspondingly move the wiper while the scale remains where last moved before removing the pressure.

5. In a rheostat, a resistor, a circuit adapted for including said resistor, a wiper for making contact along the resistor so as to introduce resistance of said resistor into the circuit, a first graduated scale for indicating the resistance included by the resistor through the agency of the wiper movement, a second movable graduated scale, a handle for operating the wiper, means for operating the= movable scale in a first stage movement by the handle coincident with operating the wiper, means for further operat1ng the wiper by the handle to introduce more resistance by the resistor without further operating the scale, and means whereby the position of the wiper with respect 130 the graduations on the movable scale will indicate the resistance inclt1ded by the resistor only by the second stage of the wiper movement.

6. In a rheostat, a resistor, a circuit adapted for including said resistor, a wiper-for makhig eontact along the resistor so as to in'troduce resistance of said resistor into the circuit, a first graduated scale for indicating the resistance included by the resistor through the agency of the wiper movement, a movable graduated scale for indicating the resistance included by the resistor through the agency of the wiper movement, a handle for operating the wiper in a first stage movement for thereby introducing resistance by the resistance included by the movable scale defined by the final position e wiper Will numerically indicate the value of the resistance included by the resistor only by the second stage movement, and means whereby the graduation on first said scale defined by the final position of the wiper will numerically indicate the total value 0f the resistance included by t-he said wiper movements.

7. In a rheostat,a resistor,a eireuit adapted for including said resistor, a wiper for inaking eontact along the resistor so as to introduce resistance 0f said resistor into the eircuit, a first graduated scale for indieating resistor through the agency of the wiper movement, a second movable graduated scale, a handle for operating the wiper, means for operating the movable seale in a first stage movement by the handle coincident with operating the wiper, means for further operating the wiper by the handle to introduee m0re re sist-anee by the resistor without further operating the scale, means whereby the position of the wiper with respect to the graduations on the movable scale will indicate the resistance included by the resistor only by the second stage of the wiper movement, and means whereby the position 0f the wiper with res ect tethe graduations on the first scale will indieate the total resistance ineluded by tl1e resistor by the said wiper movements.

8. In a measuring instrument, a rheostat, a gyrating wiper for making eontaet; along the resistor constituting the rheostat to alter the eifective resistance of the rheostat, a circular graduated scale for indicating the re sistance included by the rheostat, a handle er operaoing said wiper, means for operating the scale to revolve it about its axis coincident with operating the wiper, means f'or further operating the wiper by the handle in a second stage movement int-roduce additional resistance into the rheostat without further operating the seale, and means whereby t-he graduations on the scale as defined by the final position of the wiper will numerically indieate the value of the resistanee introdnced in the rheostat only by the second stage of its movement.

9. In a Wheatstone bridge for executing a Varley loop test, a handle f0r operating the rheostat constituting the adjustable arm of the bridge, a movable scale 0f the rheostat, means for operating the movable seale by the handle, a current indicator for demoting a balanced condition of the bridge and loop under test, means responsive' t0 the handle for bringing about the two diflerent balance conditions of the Varley loop test indicatedby the indicator, means whereby the scale Will be operated only While the handle is operated to bring about the first one 0f said balance eonditions, and means Whereby the position assumed by the handle with relation t0 the scale 00 bring about the second one of said balance eonditions Will be a decimal function ofthe resistarice in oluus fron'1 the bridge out to the fault on tl1e faulty conductor of the loop under test.

10. In a WVheatstone bridge for executing a Varley loop test, a handle for operating the rheostat eonstituting the adjustahle arm 0f the bridge, a movable graduated seale 0f the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a halanced condition of the bridge and loop undert-est, means responsive t0 the handle for bringing about the two dif ferent balance conditions of the Varley loop test indicated by t-he indicator, means Wlll@- by the scale Will be operated only while the handle is operated to bring about the first one of said balance conditions, and meaus' whereby the position assumed by the handle with relation t0 the scale to bring about the second one 0f said balance conditions Will be a numerical function in a power elf ten of' the resistance in ohms from the bridge out to the fault on the faulty conductor 0f the loop under test. 11. In a Vheatstone bridge for executing a Varley loop test, a handle for operating the rheostat constituting the adjustable arm 0f the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the'handle, a curr ent indieator for denoting a balanced condition of the bridge and loop under test, means responsive to the handle f0r bringing about t-he two different balanee eonditions of. the Varley loop test indicated by the indieator, means whereby the scale will be operated only While tl1e handle is nperated L0 bring about the lirst one of said balance couditious, and means Whereby the posiiion aesuu1ed by the handle wil relation t0 the scale t0 bring about ihe aer- 0nd one of said balance conditions Will be an even multiple of the resistauce in ohms 1"]em 7 11 the bridge out t0 the fault 0n the faulty couductor 0f the loop under test.

12. In a WVheatstone bridge for executing a Varley loop test, a handle and rigidly C011- nected pointer therefor for operating the rheostat constituting the adjustable arm of the bridge, an X-faulty post at the outer end 0f said adjustable arm, a movable scale of the rheost'at cooperative With tl1e pointer, means f0r operating the movable scale by the handle, a source 0f testing current, a cur rent indieater f0r denoting a balnced coudition 0f ehe bridge and loop under test, a switch for changing the battery connection from the X-faulty 7 I ply the battery through the ratio aians in brauch over the loop to the point of ground fault, means responsive t0 the operation of the handle for bringing about said operation of the swit ch and for also bringing about two p0s :t to ground so as to ap- 'be operated only while the handle is operated to bring about the first one of'said balance conditions, and means whereby the numerical position assumed by the pointer with relation to the scale to bring about the second one f said balance conditions will be a function in a power of ten of the resistance in ohms from the bridge X-faulty post' out to the fault on the faulty conductor of the loop under test.

13. In a Wheatstone bridge for executing a Varley loop test, a handle and rigidly counected pointer therefor for operating the rheostat constituting the adjustablearm of the bridge an X-faulty post at the outer encl of said adjustable arm, a movable scale of the rheostat c0operative with the pointer, means for operating the movable scale by the handle, a sourceof testing current, a current indicator for denoting a balanced condition of'the bridge and loop under test, a switch for changing the battery connection from the X-faulty post to ground so as to apply the battery through the ratio arms in brauch over the loop to the point of fault, means responsive to the operation of the handle for bringing about said operation of the switch and for also bringing about two .dilferentbalance conditions bf the Varley loop test indicated by the indicatdr, means whereby the scale and also the switch will be operated only while the handle is operated to bring about the first one of said balance conditiohs, and means whereby the numerical p osition assumed by the pointer with relation to the scale 130 bring about the second one of said balance conditions will be an even numerical multiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loop under test.

14. In a rheostat, a resistor, a circuit adapted 'f 01' including said resistor, a wiper for making contact along the resistor so as t0 introduce resistance of said resistor into the circuit, agraduated scale for indicating the resistanee included by the resistor through the agency 0f the wiper movement, a handle for operating said wiper, means for operating the scale by the handle coincident with operating the wiper, means for further operating the wiper by the handle in a second stage movement t0 introduce m0re resistance by the resistorwithout further operating the scale, and meanswhereby the graduations on said scale as defined by the final position of the wiper will numerically indicate 'th value of the resistance introduced by the resistor only by the second stage of the movement, last said means involving a circuit changing switch operated by the handle coincident with operating the scale.

1,sss,seo

15. In a Wheatstone bridge for executing a Varley loop test, a handle for operatirig the rheostat constituting the adjustable arm of the bridge, a movable graduated scale 0f the rheosta't, means for operating the movable scale by the handle, a current indicator for denoting a 4 balanced condition of the bridge and loop under test, means responsive to the handle for bringing about the two different balance conditions of the Vaxley loop test indicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring about the first one of said balance conditions, means Whereby the position assumed by the handle with relation to the.'scale to bring about the second one 0f said balance conditions will be an even multiple of the resistance in ohms from the bridge out to the fault on the faulty eonductor of the loop under test, last three means involving a structure consisting of a resistor for said rheostat, a first hollow shaft, a second shaft slidable within said first shaft. a wiper for said first shaft cooperative with said resistor for varying the elfective resistance value of said resistor, a circuit closing switch for said rheostat operated by said second shaft and a common handle for operating said shafts whereby the resistance value of said resistor may be varied at will and the said switch may be operated at will independent of each other.

16. In a Wheatstone bridge for executing a Varley loop test, a handle f0r operating the rheostat constituting the adjustable arm Cf the bridge a movable graduated scale of the rheostat, m-eansfor operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means res onsive to the handle for bringing about t e two different balance conditions of the Varley looptest indicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring about the first one of said balance conditions, means whereby the position assumed by the handle with relation to the scale to bring about the second one of said balance conditions will be an even multiple of the resistance in ohms fr0m the bridge out to the fault on the fau lty conductor of the loop under test last three means involving a sistor for said rheostat, a first hollow shaft, a second shaft slidable within said first shaft, a wiper for said first shaft cooperative with structure consisting cf a resaid resistor, for varying the eifective re- 17. In a Wheatstone bridge for executing a 1 and a common handle for op- Varley loop test, a handle for operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means responsive to the handle f0r bringing about the two difl'erent balance conditions of the Varley loop fest indicated by the indicator, means whereby the scale will be operated only While the handle is o perated to bring about the first one of said balance conditions, means whereby the position assumed by the handle with relation to the scale to bring about the second one of said balance conditions will be an even 1'nultiple of the resistance in ohms from the bridge out to the fault on the faulty conductor 0f the loop under test,last three means involving a structure consisting of a resistor for sa1d rheostat, a first hollow shaft, a second s'haft slidable within said first shaft, a wiper for said first shaft cooperative with said resistor for varying the effective resistance value of said resistor, a circuit changing switch for said rheostat operated by said second shaft, a common handle for operating said shafts, and means for operating the handle in one manner for varying the resistance value of the resistor and in another manner for operating the switch.

18. In a Wheatstone bridge for executing a Varley loop test a handle f0r operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means responsive to the handle for bringing abont the two different balance conditi0ns of the Varley loop test indicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring aboi1t the first one 0f said balance conditions, means whereby the position assum'ed by the handle With relation t0 the scale to bring aboutthe second one of said balance conditions will be an even multiple of the resistance in ohms from the brid;ze out to the fault on the faulty conductor of the loop under test, last three means involving structure c onsisting o:f a resistor for said rheostat, a first hollow shaft, a second shaft slidable within said first shaft, a wiper for said first shaft cooperative with said resistor for vary1ng the effective resistance value of said res1stor, a c1rcu1t chang1ng sw1t@h for said rheostat operated by said second Shaft. a

common handle for operatin.q said shafts, means for onerating the handle in one manner for varying the resistance value of the resistor'and in another manner for operating the switch, and means for operating the handle for varying the resistance value of the resistor by a rotary movement and for operating the switch by an endwise movement.

19. In a Wheatstone bridge for executing a Varley loop test, a handle f0r operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition 0f the bridg'e and loop under test, means responsive 130 the handle for bringing about the two diflerent balance conditions of the Varley loop fest indicated by the indicator means whereby the scale Will be operated only while the handle is operated to bring about the first one of said balance conditions, means whereby the position assurned by the handle with relation to the scale to bring about the second one 0f said balance conditions will be an even multiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loop under test, last three means involving structure consisting of a resistor for said rheostat, a first hollow shaft, a second shaft slidable within said first shaft, a wiper for said first shaft cooperative with said iesistor for varying the eifective resistance value of said resistor. a circuit changing switch for said rheostat operated by said second shaft, a common handle f0r operating the shafts, means for operating the handle in one manner for varying the resistance value 0f the resistor and in another manner for operating the switch, means for operating the handle for varying the resistance value '0f the resistor by a rotary movement and for operating the switch by an endwise movement, and means for at will efl'ecting both said move ments simultaneously fr simultaneously 'varying the said resistance value and operating said switch.

20. In a Wheatstone bridge for executing a Varley loop test a handle for operating the rheostat constituting the adjustable arm 0f the bridge, a movable graduated scale of the rheos'tat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and lobp under test, means responsive to the handle3for bringing about the two different balance coi1ditions 0f the Varley loop test indicaed by the indicator, means Whereby the scale will be operated only while the handle is operated to bring about the firsfi one 01 said balance conditions, means Whereby the position .assumed by the handle with relation to the scale to bring about the second one of said balance conditions will be an even multiple of the resistance in ohms frorn the bridge out to the fault on the faulty con ductor of the loop under test, last three means involving structure consisting of a resistor for said rheostat, a first hollow shaft slidable Within said first shaft, a wiper for said first 1 sistor, a circuit changing'switch for said said rotary movement.

rheostat cooperative with the end of said second shaft, and a common handle fr operating said first shaft in a rotary direct1on to alter the value of the resistor er to operate said second shaft endwise to operate the said switch.

21. In a Wheatstone bridge f0r executii1g a Varley loop test, a handle for operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale of the rheostat, means f0r operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means responsive to the handle for bringing about the two difl'erent balance conditionsof the Varley loop test indicated by the indicator, means whereby the scale will be Operated only while the handle is operated to bring about the first one of said balance conditions, means whereby the position assumed by the handle with relation to the scale t0 bring about the second one of said bala1ice conditions Will be an even multiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loop under test, last three means involving structure consisting of a resistor for said rheostat, a first hollow shaft, a sejcond shaft slidable within said first shaft, a wiper f0r said shaft cooperative with said resistor for' varying the efl'ectiire resistance value 0f said resistor, a circuit changingswitch f0r said rheostat cooperative with the end of said second shaft, a common handle for operating said first shaft in a rotary direction to alter the Value pf the resistoror to operate said second shaft endwise to operate the said switeh, and means Whereby said endwise movement may be made without eflt'ectinf;

22. In a Wheatstone bridge for executing a Varley loop test, a handle for operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale 0f the rheostat, means for operating the movable scale by the handle, a Qurrent indicator for denoting a balanced condition 0f the bridge and loop under test, means responsive to the handle for bringing about the two diflerent balance conditins of the Varley loop test indicated by the indicator, means whereby the scalewill be operated only while the handle is op erated to bring about the first one of said balanc e conditions, means whereby the position assumed by the handle with relation to the scale to bring about the second one of said balance conditions will be an even mul-.

-tiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loop under test, last three means involving a structure consisting of a resistor for, -said rheostat, a first hollow shaft, a second sistor for varying the eflective resistance value of said resistor, a circuit changing switch for said rheostat cooperative with the end of said second shaft, a common handle for operating said first shaft in arotary direction to alter the value of the resistor or to operate said second shaft endwise to operate the said switch, and means whereby said rotary movement may be made without effectin% said endwise movement.

23. n a Wheatstone bridge for executing a Varley loop test, a handle for operating the rheostat constituting the adjustable arm of the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means responsive to the handle for bringing about the two different balance conditions of the Varley loop test indicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring about the first one v -wiper for said first shaft cooperative with said resistor for varying the efl'ective resistance value of said reSist0r, a circuit changing switch for' said rheostaLt cooperativ'e with the end of said second shaft, a common handle for operati ng said first shaft in a rotary direction to alter the value ofthe resistor or to op erate said second shaft endwis'e to operate the said switch, and means whereby both said movements n1ay be made simultai1e0usly to simultaneously operate the wiper to vary the elfective value of the resistor and to operate the sWit0h.

24. In a Wheatstorie brid e for executing a Varley loop test, a handle %or operating the rheostat constituting the adjustible arm of the bridge, a movable graduated scale of the rheostat, means for operating' the movable scale by the handle, a current indicator for denoting a balanced condition of thebridge and lqop under test, means responsive to the handle for bringing about the tw0 diiferent balance conditions of the Varley loop test indicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring about the first one of said balance conditions, means whereby the position assumed by the handle with relation to the scale to bring about the second one of said balance conditions will be an even multiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loo p under test, last three means involving a structure con sistin g of a resistor for said rheostat, a shaft, a wiper on said shaft for modifying the effective resistance ofthe resistor, a scale corresponding t0 said resistor, a pointer cooperative with said scale rigidly connected with said wiper through the shaf't to indicate tl1e efitective resistance value included by said resistor, and means f0r moving said scale by said shaft while moving said wiper over only certain portions 0f the resistor so that the pointer will indicate the value 0f the elfective resistance inclucled b y the resistor modified in a predetermined manner from that actually included.

25. In a Wheatstone bridge for executing a Varley loop test, a handle f0r operating the rheostat constituting the adjus table arm of the bridge, a movable graduated scale of the rheostat, means for operating the movable scale by the handle, a current indicator for denoting a balanced condition of the bridge and loop under test, means responsive t0 the handle for bringing about the two difl'erent balance conditions of the Varley loop test in dicated by the indicator, means whereby the scale will be operated only while the handle is operated to bring about the first one of said balance conditions, means whereb-y the position assumed by ehe handle with relation to the sCale to bring about the second one of said balance conditions will be an even multiple of the resistance in ohms from the bridge out to the fault on the faulty conductor of the loop under test, last three means involving a structure consisting of a resistor fox" said rheostat, a shaft, a wiper on said shaft operv ated for modifying the eflective resistance of the resistor, a pointer rigidly moved with the shaft and wiper, a scale cooperative with said pointer for indicating t-he position of said wiper, a handle, an auxiliary circuit changing switch, and means for difl'erently operating said handle for at Will effectively operating only the wiper or at will operating only the switch.

In witness whereof, I hereunto subscribe my name this eighth day 0f J uly, 1926.

HERBERT M. FRIENDLY. 

